The present invention relates to a lighting device and more particularly to an LED lighting device in which one or more LEDs are contained within a rigid, sealed container containing a liquid coolant. The container may be an Edison-type light bulb.
For many LED applications, it is important to remove heat generated by the LED. For such reason, LEDs are typically mounted on a metal substrate and the substrate is mounted on a heat sink with cooling fins. A fan can then be used to blow air over the heat sink fins to cool the LED chip.
However, due to the relatively large distance between the LED chip and the heat sink fins, the cooling efficiency is usually low. As a result, the LED junction operates at higher temperatures, which reduces the light output and lifetime of the LED chip.
My prior U.S. patent application Ser. No. 13/092,112 discloses an LED lamp which includes a sealed housing containing an LED. The housing is filled with a liquid coolant which is in contact with the LED and the heat sink on which the LED package is mounted. When the lamp is turned on, the liquid coolant cools the LED element, thereby providing higher light output and increased lifetime of the LED element.
As the LED continues to operate, the liquid heats up and expands in volume. In the case of a rigid housing such as a glass light bulb, such expansion could cause the bulb to crack or break. To compensate, my prior invention employs an enclosure containing compressible material, which is positioned within the bulb. The enclosure containing the compressible material compresses in response to expansion of the liquid coolant as the liquid absorbs heat from the LED element.